int vtime(struct tm *, const char *, int);

enum vtime_flags {
	VTIME_START_SUNDAY = 1
};

#ifdef VTIME_IMPL
static const char * vtime_next_word(const char *);
static const char * vtime_relative3(struct tm *, const char *, const int);
static const char * vtime_relative2(struct tm *, const char *);

static const char* vtime_day_names[] = {
	"sunday", "monday", "tuesday", "wednesday", "thursday", "friday", "saturday"
};

int
vtime(struct tm *tm, const char *fmt, int flags)
{
	int i, j, k;
	const char *pnt;
	for (; *fmt; fmt++) {
		if (isblank(*fmt))
			continue;

		/* Do relative 1 */
		if (*fmt == '+' || *fmt == '-') {
			i = isdigit(fmt[1]) ? 0 : 1;
			pnt = fmt+1;
			while (isdigit(*pnt))
				i = i * 10 + (*(pnt++) - '0');
			if (fmt[0] == '-')
				i = -i;

			switch (tolower(*pnt)) {
			case 'w':
				i *= 7;
				/* FALLTHROUGH */
			case 'd':
				tm->tm_mday += i;
				break;
			case 'm':
				tm->tm_mon += i;
				break;
			case 'y':
				tm->tm_year += i;
				break;
			default:
				return 1;
			}

			fmt = pnt;
			/* No day-time savings. We want the same relative hh:mm */
			tm->tm_isdst = -1;
			mktime(tm);
			continue;
		}

		/* Absolute 1 */
		if (isdigit(fmt[0])) {
			i = j = k = -1;
vtime_abs:
			k = j;
			j = i;
			for (i = 0; isdigit(*fmt); fmt++)
				i = i * 10 + (*fmt - '0');

			if (!isblank(*fmt) && fmt[0]) {
				fmt++;
				goto vtime_abs;
			}

			if (k != -1)
				tm->tm_year = k + (k < 100 ? (tm->tm_year / 100 * 100) : -1900);

			tm->tm_mon = (j == -1) ? tm->tm_mon : j-1;
			tm->tm_mday = i;

			/* No day-time savings. We want the same relative hh:mm */
			tm->tm_isdst = -1;
			mktime(tm);
			continue;
		}

		switch (tolower(fmt[0])) {
			case 'f':
			case 's':
			case 'b':
			case 'e':
				fmt = vtime_relative3(tm, fmt, flags & VTIME_START_SUNDAY);
				if (fmt == NULL)
					return 1;
				break;
			case 'p':
			case 'l':
			case 'n':
			case 't':
				fmt = vtime_relative2(tm, fmt);
				if (fmt == NULL)
					return 1;
				break;
			default:
				return 1;
		}
	}

	return 0;
}

static const char *
vtime_relative2(struct tm *tm, const char *s)
{
	size_t len;
	int i, next = (s[0] == 'n') || (s[0] == 't');
	const char *day = vtime_next_word(s);
	if (!day[0])
		return NULL;

	for (len = 0; day[len] && !isblank(day[len]); len++);

	for (i = 0; i < 7; i++) {
		if (!strncasecmp(day, vtime_day_names[i], len))
			break;
	}

	/* TODO: Could change to words like month/week/year/day */
	if (i == 7)
		return NULL;

	if (next)
		i = ((i + 13 - tm->tm_wday) % 7) + 1;
	else
		i = - (((tm->tm_wday - i + 13) % 7) + 1);

	tm->tm_mday += i;
	/* No day-time savings. We want the same relative hh:mm */
	tm->tm_isdst = -1;
	mktime(tm);


	for (s = day; s[1] && !isblank(s[1]); s++);
	return s;
}

static const char *
vtime_relative3(struct tm *tm, const char *s, const int startSun)
{
	int i, toend = tolower(s[0]) == 'e';
	const char *type = vtime_next_word(s);
	switch (tolower(*type)) {
		case 'w':
			i = tm->tm_wday;
			if (!startSun)
				i = (i + 6) % 7;
			tm->tm_mday += - i + 6 * toend;
			break;
		case 'm':
			tm->tm_mday = 1;
			if (toend) {
				tm->tm_mon++;
				tm->tm_mday = 0;
			}
			break;
		case 'y':
			tm->tm_mday = 1;
			tm->tm_mon = 0;
			if (toend) {
				tm->tm_year++;
				tm->tm_mday = 0;
			}
			break;
		default:
			return NULL;
	}
	/* No day-time savings. We want the same relative hh:mm */
	tm->tm_isdst = -1;
	mktime(tm);


	for (s = type; s[1] && !isblank(s[1]); s++);
	return s;
}

static const char *
vtime_next_word(const char *s)
{
	while (*s && !isblank(*s))
		s++;

	while (isblank(*s))
		s++;

	return s;
}
#endif